Mixtures and Solutions is a 5-6th grade kit. It aims to introduce students to some fundamental ideas in chemistry:
- By understanding the composition of substances we can
  - understand how things go together.
  - figure out how things can be taken apart.
- Learning about changes in substances we can
  - control changes to produce new materials.
  - use changes to produce energy to run machines.
The kit is divided into four investigations:
- Separating Mixtures - Mixtures of water and solid materials are made and are separated using screens, filters and evaporation.
- Reaching Saturation - Saturated solutions of salt and citric acid are made, and comparisons of solubility of the two substances are made.
- Concentration - Solutions of different concentrations are made and compared using a balance.
- Fizz Quiz - Mixtures of solid materials and water are made. Observations of gas and precipitate formation are identified as chemical reactions.
Additional materials not provided by the kit:
- white vinegar
- chalk
Safety Notes:
- Be sure to make sure that you impress upon the students the importance of NOT EATING/TASTING the chemicals is. Some kids will think things are really sugar or try to eat the diatomaceous earth or think its cool to see how many salt crystals they can eat. Consider yourself forewarned.
- Make the students wear goggles when they use the chemicals in this kit! They are provided in a container separate from the kit boxes, and they are important for safety reasons. -newbie fellow Kai Blaisdell

Restocking Notes

Possible Lesson Plan

Kits tend to have more lessons than we have time to get through. Some lessons can be combined with others, or omitted entirely. Here is where we can suggest the 10 or so lessons for fellows to get through.
- Day 1: Investigation 1.1
- (Omit Investigation 1.2)
- Day 2: Investigation 1.3 (if evaporations are ready; otherwise wait until another day)
  - you may also wait and combine this with Investigation 2.4.
- Day 3: Investigation 1.4
- Day 4: Investigation 2.1
- Day 5: Investigation 2.2
- Day 6: Investigation 2.3
- Day 7: Investigation 2.4
  - This may be a good lesson to do as a work sample.
- Day 8:

Investigations

Investigation 1: Separating Mixtures

Investigation 1.1: Making and Separating Mixtures

Typical Duration: 50 minutes

Overview:Students learn what a mixture is, how to create and separate mixtures.
- Students observe what happens when water is added to dry samples of gravel, diatomaceous earth, and salt.
- Students determine how to separate the three mixtures they made using screens, coffee filters, and evaporation.
Preparation
- Practice setting up funnel stand and filter
- Get water
- Set up materials station with screens, funnels, filters, etc
- Set up chemical storehouse with diatomaceous earth, salt, and gravel
Advice
- As with all the investigations in this kit, we use a lot of cups for making and separating mixtures/solutions. After each lesson have the students take all their cups and: return unused material/chemicals, dump liquids in the sinks, *rinse* out each of the cups, and *dry* the cups. It's important to have dry and clean cups for the following lessons and for the following classes. There aren't enough cups for multiple classes, so they must be reused, or extra cups must be provided by the school.
- The coffee filters sometimes are too porous to effectively filter out the diatomaceous earth. Sometimes the water is a little murky after filtration, and sometimes it is very murky. If this is the case, you can make some fluted filter paper out of brown paper towels. Cut them into circles, and follow these instructions to fold a piece of fluted filter paper. (Note: it might be a good idea to make a few of these yourself for the less coordinated students.) This yields much clearer water, but might be a little slow. Be prepared to have something else to do (view diatoms, a demo, discussion, etc.) while waiting on the filtration.
Demo ideas
- Polyacrylate demo
Media Clips and Links
Extensions
- Other useful additions to this lesson.

Investigation 1.2: Separating a Salt Solution

Typical Duration: 45 minutes

Overview:Students learn how to weigh water and a salt solution, and how to separate the salt from the salt water solution.
- Students learn how to use balances.
- Students compare the mass of water with and without salt.
- Students evaporate the water from the salt solution.
Preparation
- Get water
- Set up a chemical storehouse with salt.
Advice
- Students will learn the difference between mass and volume:
  - Mass = the amount of matter("stuff") in something.
    - Measured in grams, kilograms, etc.
    - Similar to weight, although not exactly the same. If you went to the moon, you would weigh less because there is less gravity, but you would have the same mass because there would be the same amount of "stuff" in you.
  - Volume = the amount of spacetaken up by the matter.
    - Measured in liters, milliliters, etc.
    - Students are probably already familiar with volume from math class. This can cause confusion, though. If you ask them, "what is volume?" they will say "length times width times height." This is how to calculate the volume of a certain shape, but it is not the concept of volume.
Demo ideas
- Mass vs. volume demo:
  - Fill one syringe with water and one with air. Have a student hold one in each hand.
    - Which one has more mass? (The water. It is heavier.)
    - Which has more volume? (They are the same: 50 mL)
Media Clips and Links
Extensions
- This lesson is a GREAT chance to work in some math. After determining how much 50mL of water weighs (50g), I like to talk a little about the metric system (1L = 1000mL, which weighs 1000g, or 1kg). Also, after students figure out how much their scoop of salt weighed, I make a t-chart of the class's data. We always see some variability, so I like to work with the class to find the mean, median, mode, and range of our data.
- Similarly, 3-digit multiplication can easily be incorporated into this lesson. You can lead the class by presenting them with a problem, "There are 128 students who each make a solution using 100 mL of water and 3 scoops of salt. What is the total mass of everyone's solutions?" Then have them identify that we need to figure our the mass of water (50 mL) and a scoop of salt. Use their numbers and solve the problem.

Investigation 1.3: Observing Crystals

Typical Duration: 35 minutes

Overview:Students observe their salt crystals after the water has evaporated.
- Students make observations of the crystals from Investigation 1.2.
- Students are introduced to the concept of a crystal.
Preparation
- Evaporate water from salt solutions in Investigation 1.2
  - Hints for quickly evaporating the water:
    - Large surface area (use the evaporation trays provided)
    - Warm place, like in a window
    - Lots of airflow (under a vent or in front of a box fan)
    - Minimum disturbance (grows bigger crystals)
- Observe crystals: look for square shape and diagonal X pattern. Make sure to emphasize the characteristics of the salt crystals as it will help reinforce the discovery of salt in other "mystery mixtures" or chemical reactions later in the kit.
Advice
- Ask the students if this salt will dissolve if water is added. Could you evaporate it again?
- This exercise could be done later. You can grow more crystals more quickly if you use the filtered saturated solutions from Investigation 2.1.
Demo ideas
Media Clips and Links
Extensions
- If you have access to a ProScope, or other microscope that will hook up to a projector, this is a great time to use it!

Investigation 1.4: Separating a Dry Mixture

This lesson is a good introduction to the scientific method. This lesson may be used as a work sample. However, you should probably not use the standard work sample sheets, as there is no data collection. An optional modification of the standard work sample sheets is as follows:

Page 1, question #2 ("Describe what you already know...") is optional. You may omit this for the sake of time.
Omit Page 3: "Collecting and Presenting Data". There is no data to collect.
Page 4: Change question #1 to something more apt, such as: "Were you able to separate the three components of the mixture? Are any of them contaminated?"
Omit Page 4, Question 2.
Page 4, Question 3 (problems and possible improvements) is an important question for this experiment.

Typical Duration: 45 minutes (Extra if used as a work sample)

Overview:Students apply knowledge from previous three lessons to separate a mixture of gravel, powder, and salt.
- Teacher challenges students to separate this new mixture.
- Students develop a plan for separation.
- Students separate mixture using screens, filters, and evaporation.
Preparation
- A quick, bulleted list of the things you will have to have prepared before yo u teach the lesson, along with any hints for their preparation.
Advice
- If you choose to perform this experiment as a work sample, have the students prepare their question, hypothesis, and tests one class period or for homework. This way the day they are meant to investigate they will be able to use the entire time as some students take longer than others to write out the prep work.
- Observing Crystals is a shorter lesson, so it may be possible to get students started on the work sample the day before.
Demo ideas
Media Clips and Links
Extensions
- Other useful additions to this lesson.

Investigation 2: Reaching Saturation

Saturation is reached when the maximum amount of a material has dissolved in a solvent, and no more will dissolve. The solubility of a particular chemical depends on what the solvent is, and also temperature.

In general, solids dissolve better in liquids at higher temperatures. Example: To make sugar dissolve in water, heat the water on the stove before adding the sugar.
In general, gases dissolve better in liquids at lower temperatures. Example: Soda goes flat when not refrigerated. This is because the dissolved carbon dioxide escapes when warmed.

NOTE: Solubility values obtained by the students are often lower than the actual values. This is probably because as you get close to saturation, it takes longer for the scoops of solid to dissolve. Don't worry about this. These experiments take long enough as it is; if you were to wait until the solution is completely saturated, it would probably take a really long time and bore the kids.

IDEA: If you have less time, divide the experments into two days. On day 1, have the students get the solutions saturated, and maybe add one more scoop of solid. Let these sit overnight to get completely saturated, then filter and weigh the saturated solutions on the second day.
- Since there's a lot to learn the first time you do this experiment, this might be a good way to divide up the concepts as well.
- You might be able to do Investigation 2.1 and 2.2 in tandem this way.

Demo Ideas: Super-saturation Demo. A jar of sodium acetate trihydrate + water has been placed in the GK-12 room (and labeled as such) along with the original container of crystallized sodium acetate trihydrate. The sodium acetate trihydrate has crystallized in the jar. Heating on a hotplate while stirring will dissolve the sodium acetate trihydrate and form a super-saturated solution. Pour a bit of the solution into a petri dish and allow it to cool. Then place it under the document camera and add a seed crystal from the original container of sodium acetate trihydrate and watch the rapid crystallization of the sodium acetate trihydrate in the petri dish. There are many videos of this on youtube.

Investigation 2.1: Salt Saturation

Typical Duration: 1 hour 30 minutes

Overview: Students investigate how much salt will dissolve in a certain amount of water.

Preparation
- Set up a chemical storehouse with salt.
- There are a lot of materials in this one. If you have them laid out and ready at first, in the order that students will need them, it will be much easier to manage.
Advice
- Some students will intuitively think that if some salt dissolves (as they learned in Investigation 1), then eventually the water will get "used up" or "tired" of the salt, and no more will dissolve.
- Ask the students what they would expect to see once no more salt will dissolve. (They will see salt grains at the bottom of the bottle). This is when the solution is saturated.
- Remind them that if all the salt dissolves, they can stop shaking the bottle, and should add another scoop of salt.
- If you omitted Investigation 1.2, you will need to show the students how to use a balance, and guide them through how to find the mass of the dissolved salt.
- First pass out water, salt, 5mL scoops, craft sticks, bottles, cups and funnels.
- While the students are working on saturating the solution, pass out filter paper, balances, and mass pieces.
- Don't focus on whether or not the students get the correct answer for the solubility of salt. Right now they are mostly learning the procedure, and the concept that a finite amount of salt will dissolve in water.
Demo ideas
Media Clips and Links
- Sodium Chloride at wikipedia
Extensions
- Eric Shamay's outdoor saturation/solution activity idea:
  - This activity demonstrates dissolving salts in water by having the students simulate water molecules and salt ions. Each student is either a water, a sodium, or a chloride. The water molecules each have to bonds that they can make by pointing with each hand to another water or a salt ion (sodium or chloride). When a sodium or chloride is pointed to by a water, then it is "dissolved." Waters can only point to ions that are close to them, otherwise they have to point to other waters.
  - Get three different colors of paper and cut them into small cards. Recommended colors are blue, orange, and yellow. Cut each paper into small cards so you end up with at least 15 of each. Hand out all the blue cards, and half as many yellow and orange cards. there should be a 1:1 ratio of yellow to orange to make complete salt pairs. The blue cards will be waters, the yellow and orange will be sodium and chlorides.
  - Have the waters spread out so that they can't touch their neighbors, and then they should be told to stand still.
  - Take a sodium-chloride pair and have them walk into the water group. Each of the closest waters will then point with one hand to one of the ions and with the other to the other ion or to a nearby water.
  - Keep introducing more salts pairs until they can't dissolve anymore. Ask about solutions, saturation, evaporation, etc.
  - Have the students switch roles so waters can be salts, and salts can be waters.

Investigation 2.2: Citric-Acid Saturation

Typical Duration: 1 hour 30 minutes

Overview: Students investigate how much citric acid will dissolve in 50mL of water.
- The main point here is that different substances have different solubilities. The question to ask is: "Will citric acid have the same solubility as salt, or will it be more or less soluble?"
- Students should be able to work more quickly than in the last investigation, because this is the same procedure.
Preparation
- Same as Inv. 2.1, except with Citric Acid instead of Salt.
Advice
- To keep all students engaged, have them take turns shaking the bottles.
- If you don't have the full 1.5 hours, have the students add the citric acid two scoops (10mL) at a time.
Demo ideas
Media Clips and Links
- Citric Acid at wikipedia. Shows the structure, etc.
Extensions
- Other useful additions to this lesson.

Investigation 2.3: The Saturation Puzzle

Typical Duration: 1 hour 30 minutes.

Overview: Students identify a mystery substance based on its solubility in water.
- Students find the solubility of the mystery substance in the same way they did in Investigations 2.1 and 2.2.
- Students use the Chemical Data Sheet to find the identity of the mystery substance.
- Students should be able to work more quickly than in the last investigation, because this is the same procedure.
Preparation
- Make 1 copy of sheet #10, Chemical Data Sheet, for each student.
Advice
- By now, the students should be pretty used to the procedure for finding solubility.
- This experiment will try the student's patience as it will take many more scoops of epsom salts that either salt or citric acid as they are previously used to.
Demo ideas
Media Clips and Links
- Magnesium Sulfate (aka epsom salts) at wikipedia.
Extensions
- Other useful additions to this lesson.

Investigation 2.4: Comparing the Crystals

Typical Duration: 35 minutes

Overview:Students observe the crystals of sodium chloride, epsom salts, and citric acid after the water has evaporated.
- Students make observations of the crystals from Investigation 2.1, 2.2, and 2.3.
- Students are introduced to the concept of a crystal.
Preparation
- Evaporate water from salt solutions in Investigation 2.1, 2.2, and 2.3
  - Hints for quickly evaporating the water:
    - Large surface area (use the evaporation trays provided)
    - Warm place, like in a window
    - Lots of airflow (under a vent or in front of a box fan)
    - Minimum disturbance (grows bigger crystals)
- Observe crystals:
  - Sodium Chloride: look for square shape and diagonal X pattern. Make sure to emphasize the characteristics of the salt crystals.
  - Epsom salts (Magnesium Sulfate): These crystals are long and needle-like.
  - Citric acid: These crystals look like flowers or snowflakes.
Advice
- Ask the students if this salt will dissolve if water is added. Could you evaporate it again?
- Dilute the saturated solutions by a factor of 2. If you use the saturated solutions, you will grow enormous crystals that take up the entire plate, and it is difficult to see single crystals (except in the case of sodium chloride).
- If you have more than one class doing this kit at a time, it is useful to have both classes share the crystals. There aren't always enough trays to put all of the crystallization dishes that you need.
Demo ideas
Media Clips and Links
Extensions
- If you have access to a ProScope, or other microscope that will hook up to a projector, this is a great time to use it!
- I had the students draw what their crystals looked like. This is one of the few lessons where there isn't any kind of worksheet for the students to use, so I made the one that can be used to look at the three types of crystals at the same time, and with and without magnification (looking at crystals.doc). Without this worksheet, I think this lesson would have taken about 15 minutes.

Investigation 3: Concentration

Investigation 3.1: Soft-Drink Recipes

Typical Duration: 40 minutes

Overview: Students get to taste kool-aid to reinforce what a dilute or concentrated solution is.
- Points of Interest:
  - Four solutions are sampled by students and they describe how two sets of them are the same or different
  - The first set has one scoop in 1L and 3 scoops in 1L
  - The second set has 2 scoops in 1L and 2 scoops in 0.5L
  - They are to decide what is their favorite/best recipe to make kool-aid
Preparation
- Kool-aid and cups will need to be purchased for this lesson.
Advice
- Kids get a little bit excited about tasting science and drinking over concentrated kool-aid, bring them outside to demonstrate what concentrated or dilute is to relieve some energy.
Demo ideas
- Showing the kids a flashy reaction where one of the reagents has been diluted demonstrates the importance of concentration in chemistry. The Elephant's Toothpaste Demo using 30% and 3% hydrogen peroxide works well.
- An alternative to the elephant's toothpaste demo is the baking soda and vinegar demo. In this case, use 100% white vinegar and 10% vinegar. The 10% solution will fizz a little, while the 100% should fizz over the sides of the cup.
Media Clips and Links
Extensions
- You can take kids outside to a foursquare court to demonstrate the difference between concentrated, dilute or saturated. Have the rules set out that students in the court are cool kool-aid molecules and should strut around as such, with the stipulation that they do not like running into other molecules. A few students in the court is a dilute solution, many students in the court is a saturated solution, the entire class in the court will make it necessary for students to step out of the court in order to avoid running into others and will as such no longer be in solution, they represent crystals of kool-aid that did not dissolve.

Investigation 3.2: Salt Concentration

Typical Duration: 45 minutes

Overview: Solutions made at different concentrations can be measured using a balance.
- Points of Interest:
  - Students will make and measure 3 solutions: 1scoop in 50mL, 3 scoops in 50mL and 3 scoops in 150mL
  - They get to decide which is the most concentrated solution
Preparation
Advice
- A discussion on how to measure the 150mL sample compared to the 50mL sample can bring out the following concepts:
  - Everything with mass has volume
  - Concentration is determined by both mass and volume
  - Density is a way scientists use to measure concentrations of solids, liquids, and gases
Demo ideas
Media Clips and Links
Extensions
- Students can learn to factor fractions with this lesson as they can take 3 out of both the numerator and denominator of the 3rd solution to make it an equivalent fraction to the 1st solution.

Investigation 3.3: Mystery Solutions

Typical Duration: 20 minutes

Overview: Students are given three solutions and are to determine how their concentrations rank
Preparation
- You will need food coloring for this lesson
Advice
- If performed with the previous lesson as the students will have all of the necessary equipment ready and already be thinking in this mindset both lessons can be fit in a 1 hour block
Demo ideas
Media Clips and Links
Extensions
- Greater than less than practice with the solutions

Investigation 4: Fizz Quiz

Investigation 4.1: Chemical Reactions

Typical Duration: 60 minutes

Overview: Students learn to follow directions to make chemical reactions, observe the reactions, and write descriptive statements about what occurred.
- Points of Interest:
  - Students mix:
    - calcium chloride and baking soda making calcium carbonate, carbon dioxide, and salt
    - calcium chloride and citric acid making a solution
    - calcium chloride and citric acid making carbon dioxide
Preparation
Advice
- Link these reactants to how we use them in day to day life
- Reinforce the use of the words Gas and Precipitate to describe the products of the chemical reactions.
- Calcium chloride is a skin irritant, be sure to explain this
- Save products from reaction 1 to perform Investigation 4.2
Demo ideas
Media Clips and Links
Extensions

Investigation 4.2: Reaction Products

Typical Duration: 30 minutes

Overview: By investigating the products of a chemical reaction we can understand what happened
- Points of Interest:
  - Calcium carbonate that had been filtered and dried will be tested with vinegar
  - The filtered solution will be evaporated and students will discover they made salt
Preparation
- A few days will be necessary for the salt to crystallize.
Advice
- This lesson really introduces the concept of conservation of mass and that this dictates all chemical reactions must be balanced
  - A good way to reinforce this idea is to remind them that they put in Calcium Chloride and Sodium Carbonate (aka Baking Soda = really Sodium hydrogen carbonate, but that just confuses matters) after showing them that they grew salt crystals (sodium chloride). Tell them that we found one compound, sodium chloride (cross out those two words), and ask what the white powder must be. Most students will follow along and realize that the powder might be calcium carbonate.
Demo ideas
Media Clips and Links
Extensions
- Other useful additions to this lesson.

Investigation 4.3: Reaction in Bag

Typical Duration: 60

Overview: Students perform reactions in a bag to identify how much gas is formed
- Points of Interest:
  - Calcium chloride and baking soda in a bag
  - Citric acid and baking soda in a bag
  - All three reactants in a bag (new precipitate Calcium Citrate)
Preparation
- A quick, bulleted list of the things you will have to have prepared before yo u teach the lesson, along with any hints for their preparation.
Advice
- Students really get excited about this experiment, so try to fit it in!
- All three reactants in a bag can sometimes be a little too much, as such the bag will pop. Make sure students keep their bags in a bin during reactions and are not shaking or prodding the bags as they fill with gas..
- The concept of a reactant and a product will be useful for this lesson
- Try to get the students to help you write out the reactants and products
- Introduce the concept that not all reactions will happen at the same rate with the delayed precipitate of Calcium Citrate in the 3rd bag
- You may want to separate this investigation into 2 days.
- It takes time for the calcium citrate to form, you may want to prepare the first say ahead of time and allow it to dry the second.

Demo ideas
Media Clips and Links
Extensions

Investigation 4.4: Choosing Your Own Investigation

Typical Duration: X minutes (or Y 1-hour class periods)

Overview: What is the main point of the lesson? (one sentence)
- Points of Interest: A brief, bulleted outline of the contents of the lesson.
Preparation
- A quick, bulleted list of the things you will have to have prepared before yo u teach the lesson, along with any hints for their preparation.
Advice
- Tips from fellows on how to best execute the lesson.
Demo ideas
Media Clips and Links
Extensions
- Other useful additions to this lesson.

Links

FOSSweb Mixtures and Solutions website. For teacher resources, click "For Parents and Teachers" (bottom left), then "Teacher Resources". There are teacher prep videos, pdfs of all the handouts, etc.
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Mixtures and Solutions tookit Created by WA State LASER program. Includes concepts; kit set up and management, teacher tips, literacy tips.

Fellows Who Have Taught This Kit:
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Mixtures and Solutions

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